Blade fastening means



June 1956 w. A. LEDWITH BLADE FASTENING MEANS Filed Sept. 8, 1950 I lnveuiaa White?- fl. beozwim CHEF/arms United States Patent 2,751,189 BLADE (FASTENING. MEAN S -Walter A. Ledwith, Glastonbury, Conn., 'assignor to United Aircraft Corporation, East Hartford, -Couu., a corporation of Delaware Application SeptemberB, 195.0, Serial N0..183,714 14 Claims. (Cl. 253-"77) .The present invention relates to means for fastening-the .blading to the supporting'discor rotor in axial flow compressors or turbines.

In certain turbine orcompressor constructions, particularly in axial-flow multistage compressors, the axial spacing of adjacent supporting structures forsuccessive stages is so close thatthe axially inserted'bladerootconstruction cannot be utilized. It will be obvious :thatsthe'conventional, axially inserted fastening, one example-of which -is the pine-tree type of bladeroot, requires, forinsertion in the supporting structure, an axial spacing at least as great as the length of the fasteningitself and generallya slightly greater lengt The :blade lock, which prevents axial movement ofthe blade after ,it is positioned on the supporting structure, makes the blade :root before insertion slightly longer than the supp rting structure. FIZhe principal object of :the present invention is .an arrangement by which to permit insertion of blade roots-in the supporting structure where the axial spacing of adjacent stages does not permit the use of conventional blade mountings. This arrangement is particularly advantageous in a built-up rotor where it would otherwise be necessary to disassemble :the :rotor for the replacement of one or more damaged blades.

Another feature of the invention is a blade mounting which will permit, if desired, the .useof-a solid or unitary rotor in which the stages 'are more closely spaced than the axial length ofzthe blade root.

Other objects 'and'advantages will be apparent from the specification .and claims, :and from the accompanying drawings which illustrate an embodiment of 'the :invention.

Fig. l is a sectional .view through a*rotor:utilizingithe blade mounting.

Fig. 2 is -a perspective view of .a part of the supporting structure and the blade construction :ready 'to be :positioned therein.

Fig 3 is a view similarto Fig. 2 showing a modification where the blades :are widely spaced circumferentially.

Fig. 4 is a fragmentary side elevation of'the-discand blade of Fig. 3 inrassembled position.

Fig. 5 is a sectional view on the line 5 5;ofFig. '4.

The invention is shown in a built-up rotor-construction :in which the successive rows of :blades are carried by separate discs 2 with :the several stacked discs bo'lted together in axial alignment bya row of bolts extending through bosses 6 arranged in a ring concentric to :the axis of the disc. in the arrangement shown, thexaxial spacing of the discs 2 issuch that the distanceaibetween adjacent discs as the periphery of the disc where :the :blade root engages the disc 513 less than the dimension :b -of :the' blade root itself. It will be obvious that the blade rootstruc- :ture herein described is applicable to other Irotor constructions, as for example to a unitary construction in which the adjacent 'discs .2 are integrally connected together.

'Theperiphery of each d c 2 has a .wide rim fi-having circumferentially spaced projection '8 defining between .2 .them .axially extending slots .10 to receive the similarly shaped blade .root 12 on the blade 14. In the arrange intent shown .in-Fig. .2 the blade hasfla platform .16 defined .by.fianges 17 projecting circumferentially from opposite The .circumferentially spaced slots 10 and blade root 12 are dovetail in shape, although other shapes of :blade rootmaybe utilized, such that the .bladerootIhas an axially extending enlargement thereon and .the slot .is .undercut .to receive the enlargement to prevent .radialtoutward movement of the ,blade relative .to the slot.

With the arrangement so .far described, the blade root -12 could be inserted endwise into the slot 10 provided the .rim 4 was suitably spaced from adjacent structures to leave ample space axially of the rim vfor the ,placingof the entire .blade .root inalignment with the slot adapted to receive it. Since this is-not always possible, the invention contemplates an arrangement by which the blade root may .be inserted :radially into the receiving slot and then moved only a shortdistance axially into locked position. accomplish this, each of the projections 8 is divided axially by :circumferentially extending grooves 18 thereby in elfeettorrninge .nurnber of axially spacedtdovetail ,projections 1-9. Ihe dovetail blade root =12 is similarly broken up by transverse :grooves .or notches 20 as deep .as the grooves 18 forming spaceddovetail projections or Wldth .to the axial dimension of the .doveta1l projections .21 .and 19 i on ;the blade root and thewdisc respectively.

With'this arrangement it will-be apparentthat the blade may beplaced :in position vby inserting it radially intothe -.dot ted line position of Fig. 1 such that the projections '21 ion the blade-root will aline up with the grooves 18 ,on-the disc. The blade s then moved axially adistance equal axially extending, tcircum-ferentially spaced blade ;root Ire- .cei-ving slots 40 :and the blade 44 has a blade root 42 adapted 11:0 ifit in :the :slot. Projections .38 On .rhe rim .and'ithe projectionsronithe blade rootrare both interrupted bytcircumferentia'l grooves 48 and 50 in the manner above @described .in .Fig. '2 and the blades are inserted in the manner above described.

in this arrangement, however, which is particularly adapted for a wider circumferential spacing ofthe blades, the blade itself has no platform corresponding ,to the platform '16 of Fig. 2. The space between-adiacent'blades after they have been positioned on the rim [is filled by filler pieces or plates 5 2,havinginwardly extendingpro- 'jections 54 corresponding in number and axial dimension to the grooves 48. In the circumferential direction, however, the projections 54 are of such a shape as to project beyond the side edges of the projections 38 and into the grooves 50 of the blade roots as shown in the dotted line in Fig. 4 thereby effectivelylockingtheblades in their operative posjitionand preventing any axial movementof the blades. ,The plates extend circumferentially from blade to blade and into engagement with adjacent ing pin 56 may be hollow to receive a locking wire 62 which extends beyond the end of the pin and may have its ends bent radially outward to fit between positioning lugs 64 on the ends of the dovetail projections 38. In

this arrangement the filler plates 52 in conjunction with the blade roots 42 form a continuous surface for the inner boundary of the gas path over the operative sections of the blades. With this arrangement the required axial spacing of adjacent rows of blades need be only slightly greater than the axial dimension of each of the individual projections making up the blade root 42. Ob-

viously, the radial dimension of adjacent discs must be 'sufficiently different to permit the insertion of the pins 56.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure 'from its spirit as defined by the following claims.

Iclaim:

1. In a blade fastening, a disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and fitting in, said slots, each of said slots being undercut to receive the root to prevent radial outward movement of the blade, said disc having circumferential grooves therein at least as deep as and intersecting said slots, and each blade root having similarly shaped notches at least as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to pro- "vide for radial insertion of the blade root into alignment with the slots, and filler pieces located between and overlying the surface of the disc between adjacent blades mounted on the disc, said filler pieces having projections on the inner surface fitting into the circumferential grooves in the disc, and means engaging said projections and disc for holding said filler pieces in position.

2. In a blade fastening, a disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and fitting in,

said slots, each of said slots being undercut to receive the root to prevent radial outward movement of the blade, said disc having circumferential grooves therein 'at least as deep as and intersecting said slots, each blade root having similarly shaped notches at least as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for radial insertion of the projections into alignment with its slot, and filler pieces located between adjacent blades and mounted on the disc, said filler pieces having projections fitting into the circumferential grooves in the disc, and means engaging said projections and disc for holding said filler pieces in position, each of said filler pieces being wide enough circumferentially to fill the space between adjacent blades on the disc.

3. In a blade fastening, a disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and fitting in, said slots, each of said slots being undercut to receive the root to prevent radial outward movement of the blade,

said disc having circumferential grooves therein at least as deep as and intersecting said slots, and each blade root having similarly shaped notches at least as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for groove in the disc,

radial insertion of the projections on said root into alignment with its slot, and filler pieces between adjacent blades having projections fitting into the circumferential grooves and of such a dimension as to project into the notches in the blade roots to prevent axial movement of the blades after they have been assembled.

4. In a blade fastening, a, disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and fitting in, said slots, each of said slots being undercut to receive the root to prevent radial outward movement of the blade, said disc having circumferential grooves therein at least as deep as and intersecting said slots, and each blade root having similarly shaped notches at least as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for radial insertion of said projections on said root into alignment with its slot, and filler pieces between adja' cent blades having projections fitting into the circumferential grooves and of such a dimension as to project into the notches in the blade roots to prevent axial movement of the blades after they have been assembled, and means engaging said projections and disc for holding said filler pieces in position on the disc.

5. In a blade fastening, a disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and fitting in, said slots, each of said slots being undercut to receive the root to prevent radial outward movement of the blade, said disc having circumferential grooves therein at least as deep as and intersecting said slots, and each blade root having similarly shaped notches at least as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for radial insertion of the said projections on the blade root into alignment with its slot, and filler pieces between adjacent blades having projections fitting into the circumferential grooves and of such a dimension as to project into the notches in the blade roots to prevent axial movement of the blades after they have been assembled, and a pin extending through said projections and through the disc for retaining the filler pieces in position.

6. In a blade fastening, a disc having an axial slot in its periphery, said slot extending the entire width of the disc, a blade having a root corresponding in shape to, and fitting in, said slot, said slot being undercut to prevent radial outward movement of the blade, said root and disc having a number of circumferentially extending matching grooves substantially the depth of the slot to provide for radial insertion of the root into the slot, said grooves in the root separating said root into a number of axially spaced root elements, the axial dimension of each of which is at least as small as the axial dimension of the associated groove in the disc.

7. In a blade fastening, a disc having an axial slot in its periphery, said slot extending the entire width of the disc, a blade having a root corresponding in shape to, and fitting in, said slot, said slot being undercut toprevent radial outward movement of the blade, said root and disc having a number of circumferentially extending matching grooves substantially the depth of the slot to provide for radial insertion of the root into the slot, said grooves in the root separating said root into a number of axially spaced root elements, the axial dimension of each of which is at least as small as the axial dimension of the associated and means engaging with said disc for locking said blade against axial movement after it is positioned in the slot.

8. In a blade fastening, a rotor having a substantially cylindrical surface, a plurality of circumferentially spaced axial slots extending the entire width of the outer surface of the disc, a plurality of blades having roots corresponding in shape to the slots in the rotor, each of said slots being undercut and each sloi receiving the root of the associated blade to prevent radial outward movement of the blade, said cylindrical surface and said blade roots having a series of matching circumferential grooves at least as deep as the slots to form spaced projections on the blade root thereby providing for radial insertion of the blade into a position such that the blade root projections may be positioned in axial alignment with the corresponding slot in the rotor, the axial dimension of each projection on the root being at least as small as the axial dimension of the associated groove in the disc and locking means on the ends of each blade root for engagement with the ends of the disc.

9. In a blade fastening, a disc having a number of circumferentially spaced axial slots extending the entire width of the disc, blades having roots corresponding in shape to, and fitting in, said slots there being one blade for each axial slot, each of said slots being undercut and each slot receiving the root of the associated blade to prevent radial outward movement of the blade, said disc having circumferential grooves at least as deep as, and intersecting, said slots, and said blade root having similarly shaped notches as deep as the slots and defining spaced projections spaced apart to correspond to the spacing of the circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for radial insertion of the blade root projection into alignment with the slots and locking means cooperating with said blade root and the disc to prevent relative axial movement after assembly is completed.

10. In a blade fastening, a disc having a number of circumferentially spaced axially extending slots, blades having roots corresponding in shape to, and received in, said slots, each of said slots being undercut and each slot receiving the root of the associated blade to prevent radial outward movement of the blade, said disc having circumferential grooves intersecting said slots, and said blade root circumferential grooves, each projection having an axial dimension at least as small as the associated groove in the disc to provide for radial insertion of the blade root projection into alignment with the slots, each blade having laterally extending flanges thereon overlying the disc and extending circumferentially far enough for engagement with a similar flange on an adjacent blade on the disc.

11. In a blade fastening, a disc having a plurality of circumferentially spaced axial slots in the outer surface extending the full width of said disc, a plurality of blades corresponding groove in the disc and root respectively, thereby providing for radial insertion ing slot in the outer surface of said disc, and thereafter for Sliding said blade axially until the projections on the root are out of circumferential alignment with the corresponding grooves in the disc.

12. In a blade fastening, a disc having a plurality of circumferentially spaced axial slots in the outer surface extending the full width of said disc, a plurality of blades having roots corresponding in cross-sectional shape to the aforementioned slots in the discs, said roots and slots being dovetailed to prevent radial outward movement of the blades, said outer surface and each blade root having a plurality of matching circumferential grooves, at least as deep as the slots, to form spaced projections on each blade root and on the outer surface of the disc, the axial dimension of each of the projections on each of the blade roots and axial dimension of the corresponding groove in the disc and root respectively, thereby providing for radial insertion of the spaced projections on the blade root into alignment with the corresponding slot in the outer surface of said disc, and thereafter sliding said blade axially until the projections on the root are out of circumferential alignment with the corresponding grooves in the disc, and an individual fastening means associated with each blade root and engaging with the disc for holding the blade against axial movement on the disc.

13. In a blade fastening, a rotor disc having a substantially cylindrical surface, a plurality of circumferentially spaced axial slots extending the entire Width of the outer slots being dovetailed to prevent radial outward movement of the blades, said cylindrical surface and said blade roots having a series of matching circumferential grooves, at

tending projections on the disc interengage and prevent radial movement of the blade, and locking means associated with each blade and engaging the disc for holding the blade in axial position after assembly with the rotor.

14. In a blade fastening, a rotor disc having a substantially cylindrical surface, a plurality of circumferentially References Cited in the file of this patent UNITED STATES PATENTS 883,890 Kieser Apr. 7, 1908 1,466,324 Wilkinson Aug. 28, 1923 1,638,639 Marsland Aug. 9, 1927 FOREIGN PATENTS 612,097 Great Britain Nov. 8, 1947 

